Starting apparatus for internal combustion engines



Aug. 23, 1938.

STARTING APPARATUS FOR INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 1 Filed June 22, 1936 y Aug. 23, 1938. A. cALLslsN 2,128,026

STARTING APPARATUS FOR INTERNAL COMBUSTION ENGINES Filed June 22, 193e 2 sheets-sheet 2 Patented Aug, 23, 1938 aizaozs STARTING 4APPARATUS ron. INTERNAL COMBUSTION ENGINES Albert Callsen, Stuttgart-Bo Robert Bosch signor to schrnkter Haftung tnangGcrmanLar Gesellschaft mitbe-- Appucation June zz, 19st, serial No. 86,634 In Germany my 5, 1935 'Ihe invention relates to starting apparatus for internal combustion engines of the type having a pinion that can screw along a threaded shaft and which, on starting, owing to its inertia is adapted for axial displacement along the threaded shaft so as to come into engagement with the toothed rim of the flywheel of an' engine.

The defect eonnected'with these pinion drives is that on the engagement of the pinion, a tooth of the same may strike against a tooth of the flywheel and bite hard, destruction of the teeth, since then the full short circuit torque of the starter presses the teeth against each other. In order again to release'and rotate the pinion, so that its teeth come into the gaps between the teeth of the flywheel, many proposals Ahave already been made, which however either do not solve the problem satisfactorily or are very inconvenient and expensive.

The object of the present invention is to overcome this diihculty in a satisfactory and simple manner. To this end, between the threaded shaft and the driving .part of the starter, a yieldable connection is provided which is alone operative on the engagement of the pinion, and on the driving part a driving member which acts on the pinion if, on engagement, a tooth thereof strikes against a tooth of the part of the engine to be engaged thereby for starting purposes.

In the drawings two methods of carrying out the invention are illustrated.

Figure 1 shows a pinion drive in section. Figure 2 is a section on the line 2-2 of Figure 1. Figure 3 a sectional view of a second form of construction.

By a is denoted the armature shaft of an elec-J tric starting motor, on which is keyed a disc b. The shaft a has at its 4end a longitudinal bore c, in which is positioned a shaft d. On this shaft d is arranged a screw-threaded sleeve e and on the sleeve a pinion f which is adapted to screw itself along the shaft. The sleeve has at its inner end a head g with angular recesses h. On the head leaf-springs i and k are fastened in the 4;, recesses and extend outwards to the edge of the .rotation of the disc disc.

l the driving shaft a which leads to the rapid sleeve e at thebeginuing of the starting, that is to say, during the engaging of the pinion. Thus the disc b. drivers m, and springs k and i, constitute a yieldable lost motion connection between and the driven shaft e. I On the disc b yet another driver n is provided 5 4which in certain cases, as willbe hereinafter described, acts on a projection o on the pinion.y The driver -n lies in the plane/in which the projectiono comes when the pinion touches the top of the toothed riin of the flywheel p. The starter works as followsz-On switching onthe starting motor the shaft a. rotates with the disc b on which are arranged the drivers m. 'I'he drivers transmit the rotation of the shaft a 15 to the springs k, and thesetransmit it further to the sleeve e to which they are fastened. The pinion, owing to its inertia. does not rotate with the sleeve but screws itself along on this.- When the teeth of the pinion come into the gaps of the teeth of the flywheel rim, the pinion engages without more ado up to the end of the lsleeve e and is coupled fast with the sleeve, so as to transmit the full torque of the starter. The springs k are at the same time curved back so far that they wholly bear on the springs i, so that now the torque of the starting motor is transmitted by both springs together. 4

1f on the engagement of the pinion a tooth strikes against a tooth on the rim of the flywheel, the pinion is prevented from moving further in the axia direction and also, together with the sleeve, prevented from rotating about the shaft, whilst the disc b further rotates. The torque exerted on the sleeve is only small because the springs 7c are alone operative. \Before the springs Ic come quite y to bear against the springs i, the driver n strikes against the projection o which in this position of the pinion lies in the plane of rotation of the peg n, and rotates the pinion by a small amount so that tooth comesopposite gap and the pinion can completely engage. Since the axial push on the pinion is only small, on account of the weak spring k, the pin ion can be released by quite a small force and an injury to the teeth of the pinion and the toothed rim of the flywheel is avoided.

Whilst the modification illustrated in Figures 1 and 2 shows one of the possible solutions, it will be appreciated that the springs and the driver n could be otherwise arranged and constructed.

In the second example illustrated in Figure 3, the pinion f is mounted on a threaded shaft q,

which has a second .thread r. On this secondv thread can screw a sleeve s which is driven by shaft on rotation thereof the starter shaft t and can move along it. On the shaft q a stop u for the sleeve and a spring v are provided between these two parts. The sleeve carries a driving member w which can act on the projection o on the pinion.

On starting, the sleeve s drives the threaded shaft q. As this rotates quite easily on a smooth engagement until the pinion is at the end of the shaft, the pressure which is exerted by the sleeve on the spring v and the stop u is quite small. If on the engagement tooth knocks against tooth the free running of the threaded shaft is hindered. Owing to this, the sleeve s screws itself forward on the thread r so that the driving member w comes into the range of the projection o on the pinion and the pinion further rotates to a gap in the toothed rim of the flywheel p. Since the spring v is only weak, the axial pressure of the pinion against the toothed rim p corresponding to the pressure of this spring is also only small, so that injury to the pinion is avoided.

I declare that what I claim is: P

1. A starting apparatus for internal combustion engines comprising a driving shaft, a rotatable screw threaded driven shaft held against longitudinal movement relative to said driving shaft, a lost motion connection between said driving and driven shafts, yieldable means in said lost motion connection between said driving and said driven shafts, an internally threaded pinion axially displaceable along said threaded driven shaft and ladapted for engagement with a toothed part of the engine `to be started, and means comprising a member directly connected to and rotatable by said driving shaft and a member carried by said pinion, said members being relatively movable longitudinally and capable of relative rotary movement and one of said members movable in a path which intersects the path of movement of the other member whereby said members engage to angularly displace said pinion about the axis of said driven shaft should the teeth thereof fail to align with said toothed part of the engine on rotation of said driven shaft and axial displacement of said pinion.

2. A starting apparatus for internal combustion engines, comprising a driving shaft, a rotatable screw threaded driven shaft held against longitudinal movement relative to said driving shaft, a lost motion connection between said driving and driven shafts, yieldable means in said lost motion connection between said driving and said driven shafts, an internally threaded pinion axially displaceable along said threaded driven I by virtue of its own inertia and adapted for engagement with a toothed part of the engine to be started, and means associated with said lost motion connection and comprising a member directly connected to and rotatable by said driving shaft and a member carried by said pinion, said members being relatively movable longitudinally and capable of relative rotary `movement and one of said members movable in a path which intersects the path of movement of the other member whereby said members engage to angularly displace said pinion about the axis of said driven shaft should the teeth of said pinion fail to align with the toothed part of the engine on rotation of said driven shaft and axial displacement of said pinion.

3. A starting apparatus for internal combustion engines, comprising a driving shaft, a screw 4threaded driven shaft co-axial therewith, a lost motion connection between said driving and said driven shaft, differential spring means including a plurality of spring members in said lost motion connection in driving relationship between said driving and said driven shafts and being successively effective, an internally threaded pinion axially displaceable along said threaded driven shaft and adapted for engagement with a toothed part of the engine to be started and means associated with said lost motion connection to angularly displace said pinion about the axis of said driven shaft should theteeth thereof fail to align with said toothed part of the engine on rotation of said driven shaft and axial displacement of said pinion.

4. A starting apparatus for internal combustion engines comprising a driving shaft, a screw threaded driven shaft co-axial therewith, a lost motion connection between said driving and said driven shafts an internally threaded pinion axially displaceable along said threaded driven shaft on rotation thereof by virtue of its own inertia and adapted for engagement with a toothed part of the engine to be started, means to angularly displace said pinion about the axis of said driven shaft should the teeth thereof fail to align with said toothed part of the engine on axial displacement of the pinion, relatively light spring means incorporated in said lost motion connection for operation until the pinion.

engages with said toothed engine part and relatively strong spring means in said lost motion connection operative solely after engagement of said pinion with said toothed part.

5. A starting apparatus for internal combustion engines, comprising adriving shaft, a screw threaded driven shaft co-axial therewith, a lost motion connection between said driving and said driven shafts, an internally threaded pinion axially displaceable along said threaded driven shaftA on rotation thereof by virtue of its own inertia and @adapted for engagement with a toothed part of the engine to be started, means to angularly displace said pinion about the axis of said driven shaft should the teeth thereof fail to align with said toothed part of the engine on axial displacement of the pinion, dual spring means in said lost motion connection including relatively light and relatively strong spring means, the relatively light spring means being operatlye until said pinion engages with said toothed part, whereupon said relatively light spring means abut against said relatively strong spring means for operation of .both after said pinion is engaged with said toothed part.

6.l A starting apparatus for internal combustion engines, comprising an externally screw threaded driven shaft, a driving shaft, one end of which has a bearing for said driven shaft, a disc on said bearing end of said driving shaft, at least one axial projection on said disc, at least one relatively light spring projecting radially of said driven shaft, at least' one relatively strong spring projecting radially from said driven shaft but in rear of said relatively light spring, an internally threaded pinion axially displaceable along said threaded driven shaft `on rotation thereof by virtue of its own inertia and adapted for engagement with a toothed part of the engine to be started and means carried by said disc for engagement with said pinion to angularly displace the latter about the axis of said driven shaft, should the teeth' of the pinion fail to engage with the toothed part of the engine to be started on displacement of the pinion through the relatively light spring and lost motion connection between the driving and the driven shafts.

A 7. A starting apparatus for internal combusa toothed part of the engine to be started, an abutment carried by said pinionfand means directly connected to and rotatable by said driving shaft and movable in a path which intersects the path of movement of said abutment whereby said means engages said abutment and angularly displaces said pinion about the axis of said driven shaft should the pinion teeth fail to align with said toothed part of the engine on rotation of said driven shaft and axial displacement o! 10 said pinion.

ALBERT CALLSEN. 

